Interleaving of base and enhancement layers for hd-dvd using alternate stream identification for enhancement layer

ABSTRACT

A method of providing multiple versions of a digital recording by using a first and second stream identification. The method can include the step of encoding a base layer having data representing a first version of a digital recording. The base layer can be encoded with a first stream identification, which can be 0xE0. The method also can include the step of encoding an enhancement layer with enhancement data which can be combined with the base data to represent a second version of the digital recording. The enhancement layer can be encoded with a second stream identification which can be 0xBF, 0xFA, 0xFB, 0xFC, 0xFD or 0xFE. The base and enhancement layers can be multiplexed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/396,397, entitled “Hybrid MPEG-2/H.26LScalability for HD-DVD” and filed Jul. 16, 2002, and U.S. ProvisionalPatent Application Ser. No. 60/430,558, entitled “Hybrid Scalable CODECFor Single Disc SD/HD-DVD” and filed Dec. 3, 2002, both of which areincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Statement of the Technical Field

The inventive arrangements relate generally to methods and apparatus forvideo systems, and more particularly to digital video disc (DVD) storagemedia.

2. Description of the Related Art

DVD (digital video disc or digital versatile disc) is an optical disctechnology which can store much more data than a CD-ROM. In particular,using conventional red laser technology, a single layer DVD can hold 4.7GB of data on each of its two sides and a dual layer DVD can hold 9.0 GBof data on each of its two sides. In comparison, a CD-ROM can holdapproximately 600 MB of data. Due to their large storage capacity andtheir convenience of use, DVD's have quickly become the preferredstorage medium for video replay, replacing both video cassettes tapesand laser discs. In particular, a typical DVD-video can hold a133-minute movie on one of its two sides using MPEG-2 file compression.The other side of the DVD oftentimes is used for DVD identification andlabeling purposes.

There are potentially two primary presentation formats for moviesrecorded on DVD's, namely standard definition (SD) which has either a16:9 or 4:3 aspect ratio, and high definition (HD) which has a 16:9aspect ratio. However, because a typical single layer DVD only can holdup to a 133 minute SD movie on a side, DVD-videos are usually providedonly with one of the two presentation formats. In some instances,however, both sides of the DVD are used to provide both presentationformats. Specifically, a standard definition version of a movie can beprovided on one side of the DVD while a high definition version of themovie could be provided on the other side. Unfortunately, when bothsides of the DVD are used for data storage, there is little room for DVDidentification and labeling. Accordingly, what is needed is a DVDstorage technology which can be used to store both SD and HD versions ofa movie on a single side of a DVD. Moreover, such a DVD should becompatible with existing SD-DVD players.

SUMMARY OF THE INVENTION

The present invention relates to a method of providing multiple versionsof a digital recording by using a first and second streamidentification. The method can include the step of encoding a base layerhaving data representing a first version of a digital recording. Thebase layer can be encoded with a first stream identification, which canbe 0xE0. The method also can include the step of encoding an enhancementlayer with enhancement data which can be combined with the base data torepresent a second version of the digital recording. The enhancementlayer can be encoded with a second stream identification which can be0xBF, 0xFA, 0xFB, 0xFC, 0xFD or 0xFE. The base and enhancement layerscan be multiplexed. For example, the base and enhancement layers can beinterleaved.

The base layer encoding can be in a format substantially similar toMPEG-2. The enhancement layer encoding can be in a format substantiallysimilar to H.264. Further, the second version of the digital recordingcan include high definition program content. The base layer and theenhancement layer can be stored on a single side of the storage medium,for example on a digital video disc (DVD).

The present invention also relates to a DVD medium. The DVD medium caninclude a base layer having base data representing a first version of adigital recording. The base layer can be encoded with a first streamidentification, which can be 0xE0. The DVD medium also can include anenhancement layer having enhancement data which can be combined with thebase data to represent a second version of the digital recording, forexample a version having high definition program content. Theenhancement layer can be encoded with a second stream identificationwhich can be 0xBF, 0xFA, 0xFB, 0xFC, 0xFD or 0xFE. Further, the base andenhancement layers can be multiplexed. For example, the base andenhancement layers can be interleaved.

The base layer and the enhancement layer can be stored on a single sideof the DVD medium. In one arrangement, the base layer and enhancementlayers can be stored on different physical layers of a multi-layer DVD.The base data can be stored in a format substantially similar to MPEG-2and the enhancement data can be provided in a format substantiallysimilar to H.264.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating hybrid scalable encoder which isuseful for understanding the present invention.

FIG. 2 is a conceptual diagram illustrating a method of interleavingstandard definition video data with enhancement video data.

FIG. 3 is a block diagram for a down-sampling algorithm usable with theencoder of FIG. 1.

FIG. 4 is a block diagram for transform coefficients usable with theencoder of FIG. 1.

FIG. 5 is a block diagram for an interpolation algorithm usable with theencoder of FIG. 1.

FIG. 6 is a block diagram illustrating hybrid scalable decoder which isuseful for understanding the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention describes a scalable videoencoding scheme that can allow multiple versions of a title, such as amovie or other presentation, to be stored on a single storage medium.For example, one standard definition (SD) version and one highdefinition (HD) version of a title can be stored on a single digitalvideo disc (DVD). In particular, SD data representing the SD version canbe coded and stored on the DVD as a base layer using a compressionscheme compatible with existing SD-DVD players, for example MPEG-2.Further, the SD version can be stored in a video stream (SD videostream) having a stream identification (SD identifier) which iscompatible with existing SD-DVD players. For example, the streamidentification assigned to the SD video stream can be 0xE0.

HD data representing the HD version of the title can be coded and storedon the DVD as an enhancement layer using a compression scheme whichprovides greater compression than MPEG-2, for example H.264. Further,the HD version can be stored in a video stream (HD video stream) thathas a stream identification (HD identifier) which is different than theSD identifier. In the preferred arrangement, the HD identifier can be anidentifier not currently used by MPEG. For instance the HD identifiercan be 0xBF, which is a stream identification reserved for privatestream 2, or the HD identifier can be in the range of 0xFA to 0xFE,which are reserved identifications. Nonetheless, the invention is not solimited as stream identifiers may change as coding standards evolve.

Accordingly, DVD's can be produced which are compatible both with SD-DVDplayers and hybrid HD-DVD players. While the base layer can be accessedby SD-DVD players, both the base and enhancement layers can be accessedby HD-DVD players. Data on the enhancement layer can be differentiatedfrom data on the base layer using the SD and HD stream identifiers.

Referring to FIG. 1, an exemplary block diagram is shown of a hybridscalable encoder (encoder) 100 which can parse an original HD sequence,such as a video title, into a base data bitstream and an enhancementdata bitstream. The encoder 100 can be realized in hardware, software,or a combination of hardware and software. For example, the encoder 100can include one or more processors which execute program code andprocess data. Such a processor can be a central processing unit (CPU), adigital signal processor (DSP), an application specific integratedcircuit (ASIC) or any other suitable processor. The encoder 100 caninclude a decomposition unit 110, a base encoder 112, an SD frame buffer114, an interpolator 116, a summing block 118, a clipper 120, an HDframe buffer 122, and an enhancement encoder 124.

The decomposition unit 110 can parse the original HD sequence into basepixels and enhancement pixels. The base pixels can be pixelsrepresenting an SD version of the sequence. The enhancement pixels canbe pixels which can be recombined with the base pixels to represent anHD version of the sequence.

The base encoder 112 can encode the base pixels into a formatrecognizable by an SD-DVD and output a base data bitstream. Similarly,the enhancement encoder 124 can encode the enhancement pixels using asuitable coding scheme and output an enhancement data bitstream. In thepreferred arrangement, the compression scheme provided by the encoders112, 124 should provide adequate coding efficiency to store both the SDdata and the enhancement data on a single side of a DVD. Accordingly,one side of the DVD can be available for labeling purposes. For example,the base encoder 112 can encode the base pixels using an MPEG-2 format.Compression schemes which can be used for coding the enhancement dataare modified versions of H.264, also known as JVT, MPEG-4 Part 10 orAVC, or any other suitable compression scheme. Although MPEG-2 also canbe used for coding the enhancement data, MPEG-2 may not provide as muchcompression as other compression schemes, such as H.264. In consequence,the use of MPEG-2 for coding the enhancement data may limit the lengthor quality of an HD version of a title stored on a DVD.

In the instance that a modified version of H.264 is used, themodification can include an extra filtering step which can be usedduring motion compensation. Further, transform coefficients can bescanned in an order that differs from the order in which transformcoefficients are scanned for non-scalable H.264. The new scan order canplace base layer coefficients representing blocks of pixels beforeassociated enhancement layer coefficients. Restrictions also can be madeon coding modes.

It should be noted that audio/video compression schemes are known to theskilled artisan. Notably, both MPEG and H.26x are evolving sets ofstandards for video and audio compression. MPEG standards are generatedby the International Organization for Standardization (ISO) and theInternational Electrotechnical Commission (IEC), and currently includeMPEG-1, MPEG-2, MPEG-4, and MPEG-7. MPEG-21 is currently underdevelopment. H.26x standards are generated by the InternationalTelecommunication Union—Telecommunication Standardization Sector (ITU-T)and currently include H.261, H.262, H.263 and H.264. Of course, videoand audio coding standards are continually evolving. Accordingly, thoseskilled in the art will recognize that the present invention is notlimited to the particular coding standards identified herein.

Continuing in FIG. 1, the SD frame buffer 114 can be a data bufferassociated with the base encoder 112 to buffer reconstructed base pixelscreated by the base encoder 112. Such reconstructed base pixels may besubsequently referenced by the base encoder 112 when generating groupsof pictures (GOP's) having predicted and bidirectional frames. Further,the SD frame buffer 114 can temporarily store the reconstructed basepixels until being forwarded to other components within the encoder 100.

The interpolator 116 can interpolate blocks of reconstructed base pixelsinto blocks of pixels that are size compatible with HD pixel blocks. Forexample, the interpolator 116 can interpolate 1 1×9 blocks ofreconstructed base pixels into 16×1 6 blocks of reconstructed basepixels. The decomposition unit 110 then can subtract the 16×16 blocks ofreconstructed base pixels from correlating blocks of pixels in theoriginal HD sequence to generate the enhancement pixels.

Further, the summing block 118 can sum the 16×16 blocks of reconstructedbase pixels with reconstructed enhancement pixel blocks generated by theenhancement encoder 124 to generate summed pixel blocks. The summedpixel blocks can be trimmed to usable values by the clipper 120. Forexample, the clipper 120 can limit 8 bit summed pixels to values between−128 and 127. The HD frame buffer 122 can buffer the summed pixel blocksfor use by the enhancement encoder 124 in creating groups of pictures inthe enhancement data bitstream.

Lastly, a data store 126 can be provided for storing the base databitstream and the enhancement data bitstream. The data store 126 can bean optical storage medium, a magnetic storage medium, a magneto-opticalstorage medium, an electronic storage medium, or any other storagemedium which can store digital data. For example, in one arrangement,the data store 126 can be a DVD. The DVD can be single layer ormulti-layer. Moreover, the DVD can contain data on one or two sides. Inanother arrangement, the data store 126 can be another storage type,such hard disc drive (HDD), RAM, and so on. In such an arrangement, thebase and enhancement data streams can be transferred to one or moreDVD's from the data store 126.

The base data bitstream can be recorded onto the DVD as a base layer andassigned a stream identification of 0xE0. The enhancement data bitsreamcan be recorded onto the DVD as an enhancement layer and assigned astream identification of 0xBF, 0xFA, 0xFB, 0xFC, 0xFD or 0xFE. Thestream identifiers can be stored in a pack header associated withphysical sectors of the DVD which are used to store the data bitstreams.

In one arrangement, the base layer and enhancement layer can bemultiplexed such that SD-DVD players can read and decode the base layerand a hybrid HD-DVD player can read and decode both layers. In anotherarrangement, the base layer and enhancement layer can be stored ondifferent physical layers of a multi-layer DVD.

In a preferred embodiment, the base layer and enhancement layer aremultiplexed by interleaving the layers. Referring to FIG. 2, videoobjects within the base layer (VOB_(B)) 205 can be divided into baseinterleave units (ILVU_(B)) and video objects within the enhancementlayer (VOB_(E)) 210 can be divided into enhancement interleave units(ILVU_(E)). Notably, each interleave unit can have one or more videoobject units (VOBU's). The base interleave units and enhancementinterleave units can be stored to the DVD in an alternating fashion tocreate a string of interleaved video objects 215. As would be apparent,it is preferred that there be an approximately equal number of baseinterleave units and enhancement interleave units. To reduce the amountof buffering and processing required to achieve seamless playback of theinterleave units, it is preferred that a playback time associated withthe base interleave units be approximately equal to a playback timeassociated with the enhancement interleave units.

For example, a video object within the base layer can compriseinterleaved video object units ILVU_(B1), ILVU_(B2), ILVU_(B3), etc.Likewise, a video object within the enhancement layer can compriseinterleaved video object units ILVU_(E1), ILVU_(E2), ILVU_(E3), and soon. In such an instance, the video object units can be interleaved intothe following order: ILVU_(B1), ILVU_(E1), ILVU_(B2), ILVU_(E2),ILVU_(B3), ILVU_(E3).

Time stamps can be added to the base layer and to the enhancement layer.For example, a first time stamp added to the base and enhancement layerscan be a decoder time stamp (DTS) which synchronizes decoding of videoto insure that the video can be played back at an appropriate time. Asecond time stamp can be a presentation time stamp (PTS) which can beused to coordinate presentation of pictures within a video stream.Accordingly, presentation of video can be synchronized with correlatingaudio portions of a title. The PTS and DTS time stamps can be stored ina header of each packetized elementary stream (PES). There can be oneheader associated with each physical sector on the storage medium. Thesetime stamps can be associated with correlating intra (I) pictures.

The seamless branching aspects of DVD typically operate by providingmultiple program chains. Each program chain can provide an alternateversion of video playback. Program chains typically contain programs,which are ordered collections of pointers to cells within video objects.Each cell can be associated with one or more interleave units. Theprogram chains can link cells together and indicate what order the cellsare to be played. Importantly, individual cells can be used by more thanone program chain.

In the present invention, at least two program chains (PGC's) can becreated, one for SD playback of the DVD, and one enhancement programchain which can be used for HD playback of the DVD. The SD program chaincan be recognizable by an SD-DVD player and can link together the cellsassociated with the base interleave units. Accordingly, the SD programchain can be used to generate an SD bitstream for playback.

The enhancement program chain can be recognized by hybrid HD-DVDplayers. In one arrangement, the enhancement program chain can beprovided without an assigned entry point. The enhancement program chaincan be designed such that the enhancement program chain can be mergedwith the SD program chain to form a hybrid program chain. The hybridprogram chain can be formed once the HD-DVD recognizes that a particulardisc is a hybrid HD-DVD. In this arrangement, the hybrid program chaincan link together the cells associated with the base interleave unitsand the cells associated with the enhancement interleave units in anorder appropriate for HD playback.

In an alternate arrangement, the enhancement program chain can linktogether the cells associated with the enhancement interleave units andcan be used to generate an enhancement bitstream. The enhancementbitstream can be merged with the SD bitstream to generate an HDbitstream for HD playback.

Referring to FIG. 3, a down-sampling algorithm 300 is shown which can beperformed by the decomposition unit to generate the base pixels.Schematically, an original HD block 310, represented as A_(16×16), canbe divided into four 8×8 sub-blocks 320, 330, 340 and 350, respectively.An 8×8 integer transform can be applied in parallel to each of thesub-blocks by the 8×8 integer transformers 321, 331, 341 and 351,respectively. Next, low-pass filtering can be performed on each of thetransformed sub-blocks by low-frequency sub-block extractors 322, 332,342 and 352, respectively. The low-pass filtering can extract the lowfrequency transform coefficients from the 8×8 sub-blocks. The low-passfiltered sub-blocks then can be zero-padded to 5×4 sub-blocks by thezero-padding blocks 323, 333, 343 and 353, respectively. Inversetransforms then can be applied to each of the zero-padded sub-blocks by5×4 inverse transformers 324, 334, 344 and 354, respectively, to providenew sub-blocks 325, 335, 345 and 355 that make up a new block 312. Aninteger transform then can be applied to the new block 312 by a 10×8integer transformer 314, which can be coupled to an 11×9 zero-padder316. The zero-padder 316 can be coupled, in turn, to an 11×9 inversetransformer 318 that provides the base layer pixels, represented asB_(11×9.)

All of the transformations shown in FIG. 3 can be coded as a singlematrix transformation, making it possible to implement the procedure asa two-step process. The two step process can comprise apost-multiplication by a first downsampling matrix for horizontaldownsampling, followed by a pre-multiplication by a second downsamplingmatrix for vertical downsampling. Alternatively, the pre-multiplicationcan be performed first, followed by the post-multiplication. This twostep decomposition provides greater flexibility in the ratio ofresolutions between the enhancement and base layers.

The matrices that are provided for the horizontal and verticaldownsampling will depend on which coefficients are coded into the baselayer. Accordingly, if the coefficient selection is adaptive, eithermultiple versions of the matrices will be required, or additionalprocessing steps will be required to complete the downsampling.

Referring now to FIG. 4, an 8×8 sub-block 400 of transform coefficientsis shown which corresponds to the sub-blocks 320, 330, 340 and 350 ofFIG. 3. The 8×8 sub-block 400 can include an upper left portion 410,which can include the most significant transform coefficients which areextracted by the low-frequency sub-block. The remaining transformcoefficients can be used to create the enhancement layer 412. In onearrangement, the upper left portion can be a 5×4 sub-block of transformcoefficients. However, the upper left portion also can be smaller than a5×4 sub-block. Accordingly, a greater portion of the 8×8 sub-block 400can be encoded in the enhancement layer using a coding scheme which ismore efficient than the coding scheme that is likely to be used for thebase layer. Further, the smaller number of base layer coefficients canbe coded to give better accuracy in the base layer for a given baselayer bit rate. Hence, these coefficients may not need to be refined inthe enhancement layer. Notably, the selection of coefficients for thebase layer can be either pre-determined or adaptive.

Referring to FIG. 5, an interpolation algorithm 500 is shown which canbe performed by the interpolator to convert blocks of reconstructed basepixels into blocks of pixels that are size compatible with HD pixelblocks. The algorithm 500 includes an 1 1×9 integer transformer 510 fortransforming the reconstructed version of B_(11×9), denoted B′_(11×9).The block 510 can be coupled to a 10×8 truncation block 512 whichtruncates pixel values in B′_(11×9). A 10×8 inverse transform block 514also can be provided that outputs an intermediate block 516. Theintermediate block 516 can include four sub-divided sub-blocks 560, 570,580 and 590, respectively. An integer transform can be applied to eachof these sub-blocks by 5×4 integer transformers 562, 572, 582 and 592,respectively. Next, the transformed sub-blocks can be zero-padded by 8×8zero-padders 564, 574, 584 and 594, respectively. The zero-paddedtransformed sub-blocks then can be inverse transformed by 8×8 inversetransformers 566, 576, 586 and 596, respectively, to form correspondingnew sub-blocks 568, 578, 588 and 598. The new sub-blocks 568, 578, 588and 598 can collectively make-up block 518, represented as B′_(16×16.)

As with the decomposition, the interpolation can be provided in twosteps using a matrix transformation. The first step can include apre-multiplication by a first interpolation matrix to interpolatevertically, and then a second step can be performed which includes apost-multiplication by a second interpolation matrix to interpolatehorizontally. This two step process provides greater flexibility in theratio of resolutions between the enhancement and base layers. Thepre-multiplication and post-multiplication can be performed in anyorder, although the order in which the multiplications are performedshould be the same for both the encoder and the decoder. Again, if thecoefficient selection is adaptive, either multiple versions of thematrices will be required, or additional processing steps will berequired to complete the interpolation.

Referring to FIG. 6, a hybrid scalable decoder (decoder) 600 is shownwhich can be used to decode the base data bitsream and the enhancementdata bitstream to generate the SD and HD video streams, which can beforwarded to one or more video displays. The decoder 600 can be realizedin hardware, software, or a combination of hardware and software. Forexample, the encoder 600 can include one or more processors whichexecute program code and processes data. Such a processor can be acentral processing unit (CPU), a digital signal processor (DSP), anapplication specific integrated circuit (ASIC) or any other suitableprocessor. The decoder 600 can include a base decoder 610, an SD framebuffer 612, an interpolator 614, an enhancement decoder 616, a summingblock 618, a clipper 620, an HD frame buffer 622, and an enhancementencoder 124.

The base decoder 610 can receive the base data bitstream, for exampleafter it has been read from a DVD by a playback interface, and decodethe base data bitstream into an uncompressed format. For example, thebase decoder 610 can decode the base data bitstream from an MPEG-2format into a luminance and chrominance video stream having SD framesformed of pixels reconstructed in the decoding process. The luminanceand chrominance video stream then can be forwarded to a display, orfurther encoded into another format, for example into an NTSC, PAL,SECAM, S-video, or any other suitable format. The base decoder 610 canbe coupled to an SD frame buffer 612 for buffering standard-definitionframes during the decoding process. The SD frame buffer 612 can furtherprovide an output suitable for an SD display.

The enhancement decoder 616 can decode an enhancement data bitstream,for example after it has been read from a DVD by a playback interface,and decode the enhancement data bitstream into an uncompressed format.For example, the enhancement decoder 616 can decode the enhancement databitstream from an H.264 format into blocks of enhancement pixels whichcan be combined with blocks of reconstructed SD pixels for use ingenerating an HD video stream.

The interpolator 614 can receive reconstructed base pixels from the basedecoder 610 and interpolate blocks of the reconstructed base pixels intoblocks of pixels that are size compatible with HD pixel blocks. Forexample, the interpolator 614 can interpolate 1 1×9 blocks of basepixels into 16×16 blocks of base pixels. The interpolation process canfollow an interpolation algorithm which is much the same as theinterpolation process described for FIG. 5.

The summing block 618 can sum blocks of base pixels generated by theinterpolator 614 with blocks of pixels generated by the enhancementencoder 616 to generate reconstructed HD frames. Pixel values within thereconstructed HD frames can be trimmed to usable values by the clipper620. For example, the clipper 620 can limit 8 bit pixels to valuesbetween −128 and 127. The HD frame buffer 622 can buffer thereconstructed HD frames for use by the enhancement decoder 616 increating the enhancement pixels during the decoding process. The HDframe buffer also can provide an output suitable for an HD display. Forexample, the output can provide a luminance and chrominance video streamhaving the reconstructed HD frames.

The present invention can be realized in hardware, software, or acombination of hardware and software. The present invention can berealized in a centralized fashion in one computer system, or in adistributed fashion where different elements are spread across severalinterconnected computer systems. Any kind of computer system or otherapparatus adapted for carrying out the methods described herein issuitable. A typical combination of hardware and software can be ageneral purpose computer system with a computer program that, when beingloaded and executed, controls the computer system such that it carriesout the methods described herein.

The present invention also can be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

This invention can be embodied in other forms without departing from thespirit or essential attributes thereof. Accordingly, reference should bemade to the following claims, rather than to the foregoingspecification, as indicating the scope of the invention.

1. A method of providing multiple versions of a digital recordingcomprising the steps of: using a first stream identification, encoding abase layer comprising base data representing a first version of adigital recording; and using a second stream identification, encoding anenhancement layer comprising enhancement data which can be combined withsaid base data to represent a second version of the digital recording.2. The method of claim 1, wherein said first stream identification is0xE0.
 3. The method of claim 1, wherein said second streamidentification is at least one value selected from the group consistingof 0xBF, 0xFA, 0xFB, 0FC, 0xFD and 0xFE.
 4. The method of claim 1,further comprising the step of multiplexing said base layer and saidenhancement layer.
 5. The method of claim 1, further comprising the stepof interleaving said base layer and said enhancement layer.
 6. Themethod of claim 1, further comprising the step of storing said baselayer and said enhancement layer on different physical layers of astorage medium.
 7. The method of claim 1, wherein said encoding saidbase layer step further comprises the step of coding said base data in aformat substantially similar to MPEG-2.
 8. The method of claim 1,wherein said encoding said enhancement layer step further comprises thestep of coding said enhancement data in a format substantially similarto at least one format selected from the group consisting of H.264. 9.The method of claim 1, wherein said second version of the digitalrecording comprises high definition program content.
 10. The method ofclaim 1, wherein said base layer and said enhancement layer are storedon a single side of said storage medium.
 11. The method of claim 1,wherein said storage medium is a digital video disc (DVD).
 12. A DVDmedium comprising: a base layer having a first stream identification andcomprising base data representing a first version of a digitalrecording; and an enhancement layer having a second streamidentification and comprising enhancement data which can be combinedwith said base data to represent a second version of said digitalrecording.
 13. The DVD medium of claim 12, wherein said first streamidentification is 0xE0.
 14. The DVD medium of claim 12, wherein saidsecond stream identification is at least one value selected from thegroup consisting of 0xBF, 0xFA, 0xFB, 0xFC, 0FD and 0xFE.
 15. The DVDmedium of claim 12, wherein said base data and said enhancement data aremultiplexed.
 16. The DVD medium of claim 12, wherein said base data andsaid enhancement data are interleaved.
 17. The DVD medium of claim 12,wherein said base data is stored in a format substantially similar toMPEG-2.
 18. The DVD medium of claim 12, wherein said enhancement data isprovided in a format substantially similar to H.264.
 19. The DVD mediumof claim 12, wherein said second version of said digital recordingcomprises high definition program content.
 20. The DVD medium of claim12, wherein said base layer and said enhancement layer are stored on asingle side of the DVD medium.
 21. The DVD medium of claim 12, whereinthe DVD medium is a multi-layer DVD, and said base layer and saidenhancement layer are stored on different physical layers of saidmulti-layer DVD.